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Subject: Biochemistry × Author: Sharma, Amit × End date: 2006 × Start date: 2002 × Type: Thesis ×
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    ThesisItemOpen Access
    Studies on the development of rancidity in stored flour of pearl millet [Pennisetum glaucum (L.) R. Br.]
    (CCSHAU, 2006) Sharma, Amit; Saharan, M.R.
    The investigation was carried out on two pearl millet hybrids viz., HHB 94 and ICMA 94222A x 78/711. The former is grey in colour and has high fat and phenols content and possesses high activity of peroxidase. Light yellow hybrid ICMA 94222A x 78/711 also has high fat content and possesses comparatively low total phenols content as well as low activity of peroxidase. Composition of flour of both hybrids was modified by differential extraction of fat and phenols. Type I and type II flour containing 40 and 60% lesser fat content (compared to control flour) whereas type III and type IV flour containing 40 and 60% lesser phenols respectively were prepared. The unmodified or modified flour was stored at 37oC at ambient relative humidity for 0, 4 or 8 days in a BOD incubator. Defatting of flour caused an increase in fat acidity ‘FA’ and free fatty acids ‘FFAs’ but showed no effect on peroxide value ‘PV’ of the flour. On the other hand, extraction of phenols decreased FA, FFAs and PV of flour of both hybrids. Values of rancidity indicators viz., FA, FFAs and PV of control as well as modified flour (all the types) of both hybrids increased with increasing storage time. FA and FFAs in flour of both the hybrids having lesser phenol content increased much faster than that had correspondingly lesser fat content. Despite a higher rate of increase, by 8th day of storage, FA and FFAs of type II and type IV flour was much less than that of type I and type II flour. There was no effect of reducing fat content of fresh flour of either of the hybrids on content of total phenols and on level of peroxidase activity. On the other hand, extraction of phenolics showed a profound inactivating effect on the enzyme activity of both the hybrids. In control flour of HHB 94 and ICMA 94222 x 78/711, very strong and strong rancid odour was detected on 8th day of storage. Removal of phenolics from flour of both the hybrids before storage reduced the intensity of off-odour developed during storage of flour. Blanching treatment was very effective for inactivating peroxidase in grains. Blanching of grains of HHB 94 for 120 seconds almost completely inactivated peroxidase. FA, FFAs and PV of fresh flour produced from grains blanched for 90 and 120 seconds was lower than that produced from untreated grains. Upon storage, FA, FFAs and PV of control flour increased with increasing time of storage whereas in flour produced from grains blanched for 120 seconds the values of these rancidity indicators virtually did not change further. Flour produced from blanched grains (type V, type VI and type VII) had lesser total phenols content than that of control flour. There was no change in the content of total phenols of lour prepared from untreated as well as treated grains upon storage. Based on results of both the experiments, it was concluded that high content of total phenols and high activity of peroxidase are responsible for generating rancid odour in stored flour rather fat content of grains.
  • Thumbnail Image
    ThesisItemOpen Access
    Studies on the development of rancidity in stored flour of pearl millet [Pennisetum glaucum (L.) R. Br.]
    (CCSHAU, 2006) Sharma, Amit; Saharan, M.R.
    The investigation was carried out on two pearl millet hybrids viz., HHB 94 and ICMA 94222A x 78/711. The former is grey in colour and has high fat and phenols content and possesses high activity of peroxidase. Light yellow hybrid ICMA 94222A x 78/711 also has high fat content and possesses comparatively low total phenols content as well as low activity of peroxidase. Composition of flour of both hybrids was modified by differential extraction of fat and phenols. Type I and type II flour containing 40 and 60% lesser fat content (compared to control flour) whereas type III and type IV flour containing 40 and 60% lesser phenols respectively were prepared. The unmodified or modified flour was stored at 37oC at ambient relative humidity for 0, 4 or 8 days in a BOD incubator. Defatting of flour caused an increase in fat acidity ‘FA’ and free fatty acids ‘FFAs’ but showed no effect on peroxide value ‘PV’ of the flour. On the other hand, extraction of phenols decreased FA, FFAs and PV of flour of both hybrids. Values of rancidity indicators viz., FA, FFAs and PV of control as well as modified flour (all the types) of both hybrids increased with increasing storage time. FA and FFAs in flour of both the hybrids having lesser phenol content increased much faster than that had correspondingly lesser fat content. Despite a higher rate of increase, by 8th day of storage, FA and FFAs of type II and type IV flour was much less than that of type I and type II flour. There was no effect of reducing fat content of fresh flour of either of the hybrids on content of total phenols and on level of peroxidase activity. On the other hand, extraction of phenolics showed a profound inactivating effect on the enzyme activity of both the hybrids. In control flour of HHB 94 and ICMA 94222 x 78/711, very strong and strong rancid odour was detected on 8th day of storage. Removal of phenolics from flour of both the hybrids before storage reduced the intensity of off-odour developed during storage of flour. Blanching treatment was very effective for inactivating peroxidase in grains. Blanching of grains of HHB 94 for 120 seconds almost completely inactivated peroxidase. FA, FFAs and PV of fresh flour produced from grains blanched for 90 and 120 seconds was lower than that produced from untreated grains. Upon storage, FA, FFAs and PV of control flour increased with increasing time of storage whereas in flour produced from grains blanched for 120 seconds the values of these rancidity indicators virtually did not change further. Flour produced from blanched grains (type V, type VI and type VII) had lesser total phenols content than that of control flour. There was no change in the content of total phenols of lour prepared from untreated as well as treated grains upon storage. Based on results of both the experiments, it was concluded that high content of total phenols and high activity of peroxidase are responsible for generating rancid odour in stored flour rather fat content of grains.